The processes for sea water desalination have been around for many years; however, these processes had very high installation and operating costs and a large consumption of energy. The first desalination plants used evaporative technologies, either Multi-Stage Flash Evaporation (MSF) or Multi-Effect Distillation (MED), Vapor Compression (VC), which represented changes in the physical state, which consume a lot of energy. These plants had an energy consumption of more than 12 kWh per cubic meter of potable water produced.
The alternative for these processes has been the development of reverse osmosis. There have been various technological changes to improve the process of reverse osmosis, initially with the use of membranes of different geometries and materials which improve the process and the design of dual processes, to harness the reject water in order to reduce energy consumption, using turbines, Francis Turbines, Pelton Turbines, and lately, the Pressure Exchanger such that in the HON Plant in the Canary Islands, in Lanzarote Spain, that have achieved energy consumptions of 2.6 kWh per cubic meter of water-product. A very respectable figure for this process.
In 1955, electrodialysis (ED) began to be applied in brackish water. These were conducted in laboratories equipped to quantify the results and make the corrections that were required to continue improving efficiency. ED uses electric power with sufficient pressure to force the passage of water with a high concentration through an ion exchange membrane.
The year 1957 marks a milestone, when a patent was simultaneously requested for a SPS module, by Silver and Frankel. With energy savings and large capacities. The first plant with these conditions was installed in 1960 in Kuwait, which produced 1560 m3/day.
The years 1958-1960 were important for reverse osmosis as Loeb and Sourirajan at the University of California. Los Angeles (UCLA), developed the membrane that became the immediate predecessor of the commercial modules.
In 1970, vapor compression began to be used commercially, with an energy consumption of up to 22 kWh./m3, and in 1978, the first large reverse osmosis plant for sea water desalination was built in Jeddah, Saudi Arabia.
Carl A. Grenci's U.S. Pat. No. 3,400,074 (1968), relates to a process for desalination of water by reverse osmosis using centrifugal force, wherein the water is introduced into a semi-permeable rotating cylindrical membrane so that the pure water passes through the membrane by the action of the centrifugal force.
Ronal Gayler Wantage's U.S. Pat. No. 3,883,434 (May 13, 1975), concerns an apparatus for rotary reverse osmosis, which comprises a diaphragm assembled in a pressure vessel. The assembly is mounted for rotation together with the vessel. During rotation, a high recovery percentage of liquid product is promoted. The flow of the turbine may be operated by feeding or by using the reject fluid.
Bowie G. Keefer's U.S. Pat. No. 4,230,564 (Oct. 20, 1980), concerning an apparatus for reverse osmosis or ultrafiltration, has two rotors turning in the same direction around the central axis, wherein the first rotor rotates at high speed and has a drive which serves the feed pump. The second rotor rotates at low speed and has a pressure vessel with a high selectivity semipermeable membrane with a component of the feed stream. This arrangement reduces the losses caused by friction. Compared with centrifugal machines with stationary covers, the membrane is set up for the action of the centrifugal force.
Thomas L. Siwecki's U.S. Pat. No. 4,333,832 (Jun. 8, 1982) concerns a process wherein the sea water and other solutions are accelerated into a rotating structure and applied to a carbon filter. Desalinated water is removed after passing through a long membrane surface, wherein the membrane arrangement is designed in two levels.
The U.S. Pat. No. 4,886,597 of Peter M. Wild., et. al., (Dec. 12, 1989) relates to centrifugal equipment for reverse osmosis desalination, wherein a feed solution containing sea water is separated into a product comprised of a solution with a reduced salt concentration and a depleted solution with an increased concentration, which includes an evacuation sheath to reduce losses due to wind exposure and energy consumption.
The publication of Francisco Sanchez Sainz's Patent WO 98/36823 (Aug. 27, 1998) refers to a centrifugal reverse osmosis system with an option to recover devices for kinetic energy of the product, the purpose of which is to save energy and reduce the cost of product of reverse osmosis processes wherein from the low pressure fluid feed stream, and through the pressure created by the centrifugal force on the module container of the semi-permeable membrane and through rotation about an axis, a product or permeate stream is obtained, thus evacuating the fluid at low pressure. Optionally, the kinetic energy of the product or permeate can be recovered using a device formed by biading and a transmission, transforming it into mechanical energy, and/or to be recovered in the form of pressure through a device formed by a spiral wrap capable of capturing the rotational flow of the product.
Recently, in 1997, Georges Belfort deepened the above principles for nano filtration and ultrafiltration through a membrane with curvature implemented through research, the arrangement of membranes proposed by Dean in 1927 that allowed the formation of vortices that received the name of Dean vortices. These vortices, present some advantages over those of Taylor USPTO patent, 1997.
The U.S. Pat. No. 6,824,679 of Stephen Dzengeleski, et. al. (Nov. 30, 2004) relates to a separation module with hollow fiber membranes and it provides methods for producing packages of one or more layers of membranes made with spiral hollow fiber, for use in separation modules whose performance can be predicted. These modules are designed to use the benefits of Dean vortices. The invention is directed to packets of multiple coiled hollow fibers for use; separation modules are directly scalable because each layer has a performance which is substantially equivalent to the other layer when subjected to flows with a certain speed such that Dean vortices develop.
The Stephen Dzengeleski patent is very similar to the work presented, since it also explores winding of the hollow fiber membranes to create Dean vortices; up to here, the similarities in terms of the differences, Dzengeleski proposes the use of a pump to print the necessary pressure fluid in order to produce reverse osmosis, while our invention proposes to use centrifugal force to promote the necessary pressure so that the reverse osmosis process occurs, with energy recovery, and strengthening of Dean vortices; one more difference, results from winding of the membranes; Dzengeleski, winds his membranes in layers of three, in our invention, we propose a winding in a quincunx manner (triangular array), which reinforce the set of membranes, for the structure formed.
It is pertinent to comment on patent number: 2299349, of Merce Vives Salvador, granted by the Spanish Office of Patents and Trademarks in 2008. The invention discloses a device for desalination, by centrifugal reverse osmosis, with the rotation of a rotating cylinder, the wall of which, is located within another revolving cylinder. It produces energy savings, although the cost is a little high and it does not have spirally wound membranes, therefore, it does not generate Dean vortices.
The process and equipment designed focus on a significant energy savings, which would permit alternative energies, such as wind, tidal, solar, etc., to be accessed and used to process sea water.